1. Field of the Invention
This invention relates to wing pylon arrangements for aircraft. More particularly it relates to extension fairings for pylons to minimise aerodynamic penalties on the wing.
2. Description of the Related Art
Both civil and military aircraft require underwing mounted pylons to carry engines, weapons and fuel tanks. The purpose of the pylon is not only to support underwing items but also carry, internally, services and accessories. The presence of underwing pylons can produce an aerodynamic penalty in the form of a loss of local wing lift. This aerodynamic penalty can be reduced by careful design of the pylon cross-section. However, this tends to result in a thin pylon with a complicated shape and, consequently, a reduction in available internal volume for the services and accessories.
One of the ideal pylon shapes for ease of manufacture, low weight and low cost is a flat-sided pylon structural box of constant thickness with a simple front and rear fairing. Its aerodynamic qualities, however, are poor. There is therefore a conflict of reqiurements between what is good for aerodynamic performance and what is beneficial for manufacture structure and costs.
It is the object of the present invention to provide an improved pylon configuration of simple construction with very little or no aerodynamic penalty relative to an aerodynamically optimum pylon.
One known prior art pylon arrangement is disclosed in U.S. Pat. No. 4,867,394 (Patterson) in which the pylon is shaped in such a way as to reduce the drag and loss of wing lift within the fuselage-wing-pylon nacelle channel of an aircraft without creating additional drag associated with other areas of the pylon. In this arrangement, the chord length of the pylon is greater than the local chord length of the wing to which it is attached. However, the cross-sectional area of the pylon progressively increases longitudinally from its leading edge to the local trailing edge of the wing and thereafter decreases longitudinally from the local trailing edge of the wing to the trailing edge of the pylon.